{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE RankNTypes #-}
module Data.Type.Coercion
( Coercion(..)
, coerceWith
, gcoerceWith
, sym
, trans
, repr
, TestCoercion(..)
) where
import qualified Data.Type.Equality as Eq
import Data.Maybe
import GHC.Enum
import GHC.Show
import GHC.Read
import GHC.Base
data Coercion a b where
Coercion :: Coercible a b => Coercion a b
coerceWith :: Coercion a b -> a -> b
coerceWith :: forall a b. Coercion a b -> a -> b
coerceWith Coercion a b
Coercion a
x = a -> b
forall a b. Coercible a b => a -> b
coerce a
x
gcoerceWith :: Coercion a b -> (Coercible a b => r) -> r
gcoerceWith :: forall {k} (a :: k) (b :: k) r.
Coercion a b -> (Coercible a b => r) -> r
gcoerceWith Coercion a b
Coercion Coercible a b => r
x = r
Coercible a b => r
x
sym :: Coercion a b -> Coercion b a
sym :: forall {k} (a :: k) (b :: k). Coercion a b -> Coercion b a
sym Coercion a b
Coercion = Coercion b a
forall {k} (a :: k) (b :: k). Coercible a b => Coercion a b
Coercion
trans :: Coercion a b -> Coercion b c -> Coercion a c
trans :: forall {k} (a :: k) (b :: k) (c :: k).
Coercion a b -> Coercion b c -> Coercion a c
trans Coercion a b
Coercion Coercion b c
Coercion = Coercion a c
forall {k} (a :: k) (b :: k). Coercible a b => Coercion a b
Coercion
repr :: (a Eq.:~: b) -> Coercion a b
repr :: forall {k} (a :: k) (b :: k). (a :~: b) -> Coercion a b
repr a :~: b
Eq.Refl = Coercion a b
forall {k} (a :: k) (b :: k). Coercible a b => Coercion a b
Coercion
deriving instance Eq (Coercion a b)
deriving instance Show (Coercion a b)
deriving instance Ord (Coercion a b)
deriving instance Coercible a b => Read (Coercion a b)
instance Coercible a b => Enum (Coercion a b) where
toEnum :: Int -> Coercion a b
toEnum Int
0 = Coercion a b
forall {k} (a :: k) (b :: k). Coercible a b => Coercion a b
Coercion
toEnum Int
_ = String -> Coercion a b
forall a. String -> a
errorWithoutStackTrace String
"Data.Type.Coercion.toEnum: bad argument"
fromEnum :: Coercion a b -> Int
fromEnum Coercion a b
Coercion = Int
0
deriving instance Coercible a b => Bounded (Coercion a b)
class TestCoercion f where
testCoercion :: f a -> f b -> Maybe (Coercion a b)
instance TestCoercion ((Eq.:~:) a) where
testCoercion :: forall (a :: k) (b :: k).
(a :~: a) -> (a :~: b) -> Maybe (Coercion a b)
testCoercion a :~: a
Eq.Refl a :~: b
Eq.Refl = Coercion a b -> Maybe (Coercion a b)
forall a. a -> Maybe a
Just Coercion a b
forall {k} (a :: k) (b :: k). Coercible a b => Coercion a b
Coercion
instance TestCoercion ((Eq.:~~:) a) where
testCoercion :: forall (a :: k) (b :: k).
(a :~~: a) -> (a :~~: b) -> Maybe (Coercion a b)
testCoercion a :~~: a
Eq.HRefl a :~~: b
Eq.HRefl = Coercion a b -> Maybe (Coercion a b)
forall a. a -> Maybe a
Just Coercion a b
forall {k} (a :: k) (b :: k). Coercible a b => Coercion a b
Coercion
instance TestCoercion (Coercion a) where
testCoercion :: forall (a :: k) (b :: k).
Coercion a a -> Coercion a b -> Maybe (Coercion a b)
testCoercion Coercion a a
Coercion Coercion a b
Coercion = Coercion a b -> Maybe (Coercion a b)
forall a. a -> Maybe a
Just Coercion a b
forall {k} (a :: k) (b :: k). Coercible a b => Coercion a b
Coercion